Acoustic foam!

[kach22i]

Hi. My wall is made of concrete. I read that reflections should be covered, but I don't know what type of acoustic panel to use. What are your opinions?

What if any acoustic problems are you experiencing?

The example below uses helmholtz diffusers in clear acrylic. Helmholtz devices normally operate in a very narrow frequency range.

My Little Barn
https://www.whatsbestforum.com/threads/my-little-barn.26426/

https://www.gearslutz.com/board/studio-building-acoustics/887772-volumetric-diffusion.html

An all concrete bunker would tend to trap the bass energy and lend to smearing stereo images if not outright exaggerate bass modes/nodes.

Some people may simply use two to four subwoofers to counter these long standing waves.

Hard surfaces in general lead to a lively room, whereas soft surfaces tend to absorb high and middle frequencies and run the risk of you having an overly dampened room that sounds dead.

If you like the way the room sounds now, then do nothing.

The nice thing about cheap foam is it is mobile and invites experimenting with location.

Large bass traps usually occupy the corners for best results.

Type of loudspeaker and dispersion pattern are a major factor.

What do you have?

What is the size of your room W x L x H?

Are all the walls concrete?

What about ceiling and floor construction?

https://acousticsfirst.info/

Your room is an acoustic system – from the sound source, to the ears of the listeners – as well as
everything in, around, and even outside of that room.

The gentleman in the link below had a concrete/block wall and wood stud wall on opposite sides and came up with a novel solution.

https://www.audionirvana.org/forum/...h-for-a-simple-solution-with-paper-thin-walls

My design works really well and can be installed over existing walls. See http://www.kosmic.us/KOSMIC Virtual Reality Wall Panels.pdf

If you have a mind for science, the stickies in this link will feed your mind.

https://www.audiosciencereview.com/forum/index.php?forums/speakers-headphones-and-room-acoustics.9/